DAMA w/random access: e.g. INMARSAT uses pure
ALOHA for request channel. OK since allocation tends to
be long-lived; no good if transmissions are bursty or
short-lived

Multiple access protocols

Slotted or pure ALOHA. Efficiency (r):
eff. channel capacity divided by capacity of
a continuous channel with same power & bandwidth. For
ALOHA, r=.18, asymptotically optimal for the special case
of small values of thruput and S/N ratio.

We can choose same spreading code for all CDMA users and the
channel will still have multiple-access capability (spread ALOHA):

Each subchannel's bits will be offset by a constant amount
g
from the previous subchannel's bits within the frame

With k subchannels, prob. that 2 bits will not
overlap is (1-1/g)^k; then total traffic
G = k/g.

Get the noise-immunity of spread-spectrum with the nice
queueing properties of slotted ALOHA.

Previous studies: no compelling evidence that there is a clear
advantage for multiple-code CDMA systems, despite their
complexity

Relevance

We can get the noise immunity of spread-spectrum together with the
queueing behavior of TDMA, by implementing wideband CDMA with a single
spreading code for all users but offsetting the channel bit sequences in
time rather than by using orthogonal codes.

Flaws

It's not clear to me why the "special case" for which plain old slotted
ALOHA is asymptotically optimal is an important special case.
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